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Lecture 4

Biology 1001A Lecture 4: Lecture 4 - Mitosis and the Eukaryotic Cell, Bio 1001A

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Western University
Biology 1001A
Scott Mac Dougall- Shackleton

Lecture 4- Mitosis and the Eukaryotic Cell September 21/2016 Chromosome segregation: Equal distribution of daughter chromosomes to each of the two cells that result from cell division. 1. Phases and main characteristics of the cell cycle. Phases: Interphase ➢ G0 phase- many cells stop dividing. ➢ G1- cell carries out its function; makes RNA, proteins, molecules; growth. ➢ S phase- DNA replication and chromosome duplication occur; continues synthesis. ➢ G2- Gap in cell cycle where growth continues; cell prepares for mitosis and cytokinesis; Continues to synthesize RNA, proteins, etc.; continues to grow; end signals mitosis. *No DNA synthesis during G1 and G2 Mitosis is the shortest phase. 2. Stages of Mitosis and Changes in Amount of DNA Mitosis Human chromosomes are diploid (2n=46; 23 pairs) Diploid means 2n, 23 pairs, 46 chromosomes. Halpoid is n. Prophase - Chromosomes begin to condense; appear as thing threads - 23 pairs of chromosomes - Mitotic spindle begins to form - Nuclear envelope breaks down at the end Prometaphase - Spindle microtubules grow from centrosomes towards centre and grab onto chromosomes - Chromosome made up of two sister chromatids held together at centromeres - Kinetochore- consists of proteins; attached to centromere; mediates attachment and movement of chromosomes along mitotic spindle. - Kinetochore microtubules bind to the kinetochores. Attach sister chromatids to microtubules. Determines outcome of mitosis Metaphase - Spindle fibres move chromosomes
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